Outdoor decks e.g., adjacent to residential buildings, such as houses, provide outdoor living space, storage space, etc. The space underneath some decks, e.g., that might be accessible from a walkout basement, may also provide outdoor living space and/or storage space. However, openings in some decks, such as openings between the deck boards, allow water, such as rainwater, snow melt, water from washing the deck, etc., to enter the space underneath these decks. In addition, the water entering the space underneath through the openings may be mixed with dirt from the deck surface.